Mouse model is widely used in biological/pharmaceutical studies, and mouse PET studies are becoming popular to help investigate tissue biology in normal and pathological states, for pharmaceutical development and evaluation, and for guiding clinical procedures for disease diagnosis, monitoring, and treatment. A critical and challenging component of mouse PET to provide useful biological information is the derivation of the input function, since tissue uptake of PET radio-marker depends on, in addition to tissue biological functions, the input function that represents the time course of PET radio-marker delivery to body tissues. In the current funding cycle, novel methods for deriving input function in mouse PET studies have been developed (both image-based and with blood samples obtained with a novel microfluidic device). Furthermore, the significance of using the derived input function to enhance the accuracy and sensitivity to biological changes has been shown. The new developments naturally lead to new potentials for quantitative mouse PET. However, In order to realize fully the impact and potentials of these developments on routine mouse PET studies, additional work is needed. In this renewal, we propose to focus on -improvement of the utility of image-based input function derivation methods to make it useful in more general cases (e.g., input function for intra-peritoneal (IP) FDG injection). Methods to extract additional physiological parameters in routine dynamic FDG/FHBG/FLT PET studies will also be developed to help further improve the accuracy and convenience of the input function derivation methods. -the development and validation of a method for sequential-tracers (FLT with FDG or FHBG with FDG) mouse PET study for measurement of multiple biological functions in a single setting. -the evaluation of the use of elastic image mapping to improve the reliability/sensitivity of longitudinal mouse PET studies for measurement of biological changes over time. The collected mouse PET data, after quality check, will be placed on a public domain website for other investigators to develop quantitative mouse PET methods. The developed and validated methods in this proposal will be implemented as server-based software for general investigators to use over the Internet for deriving input functions for their mouse PET studies. Results from the proposed study are expected to enhance further the capability of mouse PET to provide quantitative biological information and to improve the reliability and sensitivity of the measurement to biological changes (physiological or due to interventions). PUBLIC HEALTH RELEVANCE: Built on top of the achievement of current grant, this proposal will further improve and extend the quantitative capability of mouse PET imaging for its wider use in biological and pharmaceutical studies. Collected data and developed methods will be made available to the public on the Internet. Results will help provide critically useful biological and pharmaceutical information that have important implication and impact to many clinical procedures in disease diagnosis, monitoring, and treatment.